Wit’s End – S Type Brake Saga

[Peterskinn]

The story so far….. 2004 S Type 2.7 D with 150K miles on the clock, failed MOT on rusty brake pipes (fixed and flexibles) and “lagging” in the operation of the brake pedal. I had already noted the classic symptoms of a failing servo (hard brake pedal and loss of braking effectiveness) so was not unduly surprised or concerned. Taking heart from the various posts on the subject from J44AEG and others I decided to tackle the job myself....

Here’s a summary of the work I did to address the “MOT” issues: -

• Replaced rear brake pipe runs with Copper Tube and new unions. In order to avoid splicing to the OEM steel pipes I replaced the entire runs including the pipes to the ABS unit.

• Replaced all four flexible pipes

• Checked with a suitable gauge the vacuum created by the engine-driven Vac pump ( -30in Hg)

• Replaced the servo unit (Pre-owned unit from Auto Reserve) - It operates exactly as it should when doing the usual engine on/engine off checks. The vacuum pipe is sound and the Non-return valve works.

• Bled the hydraulic system using a “Tyre Pressure” Gunson Bleeding machine starting with the M Cyl nipple, progressing to the rear LH brake (furthest from the master cylinder) and working round the front RH (nearest to M Cyl)

• On completion of bleeding the bleeding the pedal felt suitably firm and system checked OK for leaks throughout - especially at the new unions. There are no visible leaks at the callipers

That’s when the trouble started!! On starting the engine, the brake pedal “goes soft” and will, under normal foot pressure, sink to the floor. The brakes will stop the car especially with a quick jab at driveway manoeuvring speeds but feel very poor at anything approaching road speeds. With the engine off the pedal again travels the normal distance and feels completely normal.

In order to address this problem, I have now changed the master cylinder from the cars original one (courtesy Auto Reserve again), suspecting worn seals, and AGAIN with a further unit when the symptoms were exactly the same after the first change. The thinking here being to eliminate the possibility of “flipped” seals in M Cyl. On both changes I have bled the hydraulic system repeatedly both with the Gunson apparatus and the old-fashioned way – with my glamorous assistant pumping the pedal as directed….

I also did a battery disconnect/reset of the EPB to see if that had any effect – it did not.

Today I bled the system again using the gunson unit and at each wheel allowed approx. 250Ml of fluid to pass through the bleed nipples before stopping. My thinking on doing it that way was to eliminate the possibility of any old fluid and or any obscure air pockets. Given that I have now consumed about 3 litres of fluid, I consider this unlikely!

The Car’s symptoms are EXACTLY the same. My symptoms include high blood pressure and a violent urge to throw spanners!

Does anybody have any ideas?? Please help before I am forced to concede defeat and scrap the car. My wife is already making disturbing noises about Volvos…..

[J44EAG]

Is there not a differential pressure relief valve between the front and rear circuits?

I had one of those fail on a 3.5 Rover SD1 and the braking was very scary. Swapped that valve out and the problem went away. Worth similar investigation?

Mike K

[Peterskinn]

Hi and thanks for your response!

TBH I don't know and have not been able to find a reference to such an item. I wonder if it's all incorporated in the ABS control??

I guess that's about the last thing to try!

If anybody has any other ideas......

[jeff1954]

Hi Have you tried bleeding the brakes with the engine running. That way you are making full use of the servo/brake booster.
Jeff

[steve_m]

I find in situations like this that it is actually easier to just change the car.

[Peterskinn]

My Thanks to all who have responded!

I will - when the spirit moves me - try to get a look at the "new" servo unit now fitted. I will also try to do another bleed and perhaps split the unions at the ABS Unit!

My wife is in FULL agreement with Steve M!!!

[andypryce]

Yup, sometimes you just have to admit defeat, hurts though!

[ptjs1]

....
My wife is in FULL agreement with Steve M!!!

Peter,

If my wife was suggesting that the car needed to go, I'd definitely consider a change.

...But I'd keep the car!

Paul

[Astromorg]

I think I'd be going back to Auto Reserve and suggesting to them that the servo they supplied has failed within their 30 day warranty period. (Even if it's overrun by a few days in the circumstances!) You've been more than diligent in pursuing every other possibility.

[steve_m]

I have had the odd thing from Autoreserve which has failed or not been up to scratch and they have been more than helpful in replacing the item; they didn't even want the failed item back, just sent a replacement out.

[Peterskinn]

An end to the saga........

VERY sadly I've sold the Jag yesterday. Tried everything and could NOT get the brakes to work. Minor point IMHO but the MOT man saw it differently!

Advertised it with no MOT and had my arm ripped off by some Romanian scrote from Manchester. I suspect it'll shortly be in Bucharest - or in pieces!

Very sad day as I have loved this car. However Head has to rule Heart and I've had 100K relatively trouble-free miles. In the end I just couldn't face any more work, on the drive, in November!

I second the comments about AutoReserve who have been helpful all the way through......

[steve_m]

Sad face emoji.